Obesity is threatening the health of an increasing number of patients. There are numerous treatments for obesity, such as diets, medical treatments and cosmetic surgery but also surgical procedures. Thus, bariatric surgery is a solution for the care of morbidly obese patients with a body mass index BMI greater than 40 or greater than 35 with a co-morbidity. Bariatric surgery consists of restricting the absorption of food, in effect reducing a patient's daily calorie intake, and thus combating obesity. It brings together a set of techniques which can be classified into two main types of intervention:                the first aim to reduce gastric capacity, i.e. the useful volume of the stomach, and/or to reduce the emptying rate of the stomach in order to more rapidly achieve a feeling of fullness. These include gastroplasty using a variable gastric ring and vertical band gastroplasty by stapling or longitudinal sleeve gastrectomy;        the second, so-called mixed type combine with this gastric restriction the creation of a bypass system in the digestive tract in order to reduce the absorption of nutritive elements by the intestine: gastric short-circuit or gastric by-pass.        
Intervention techniques of the second type are implemented mainly after other medical therapies have failed. Longitudinal sleeve gastrectomy as well as gastric by-pass operations are very popular because they give good results in terms of weight loss. However, in recent years, patients having undergone a gastric by-pass operation some ten years previously have been found to put weight back on. This is explained by the fact that, over the course of time, the stomach becomes dilated. As the longitudinal sleeve gastrectomy operation is more recent, the scientific community still lacks the necessary retrospective view to determine the developments and consequences of this operation, but this same problem of dilation may justifiably be feared.
For these two operations the need to limit the dilation of the stomach and to calibrate the stomach therefore appears to be of the utmost importance.
It is known, for example from patent applications FR 2 799 118, FR 2 799 118, FR 2 981 265, EP 0 611 561, WO 94/27504, WO 2004/019671, to use gastric rings that can be inflated with a physiological liquid thus making it possible to restrict the stomach and thus reduce its diameter. However, suitable inflation of the ring is a delicate and relatively complex operation. Furthermore, it requires a sub-cutaneous module involving risks of leakage and contamination.
Documents WO 02/096326, FR 2 896 148 and WO 2005/072195 make it possible to overcome these drawbacks by proposing gastric rings without an inflatable portion. However, these devices also have numerous drawbacks:                the inner diameter that they provide in the closed position cannot be adjusted, which results in significant costs because rings of different sizes have to be produced,        they are rigid or semi-rigid in structure and are not well tolerated by the patient (inclusion phenomenon),        they are difficult to fit around the stomach which results in risks for the patient,        and/or they are provided with thick and/or protruding closing systems which risk injuring the area around the stomach or the stomach itself during the fitting of the ring, or once the ring has been fitted.        